How to load up CSS files using Javascript?

Is it possible to import css stylesheets into a html page using Javascript? If so, how can it be done? P.S the javascript will be hosted on my site, but I want users to be able to put in the <head> tag of their website, and it should be able to import a css file hosted on my server into the current web page. (both the css file and the javascript file will be hosted on my server). Answer Here’s the “old school” way of doing it, which hopefully works across all browsers. In theory, you would use setAttribute unfortunately